Saw-tooth oscillator



H. BAHRING 2,308,9(m

SAW-TOOTH OSCILLATOR Filed Aug. 29, 1940 2 Sheets-Sheet l Jan. 19, 1943.H. BAHRING 2,303,908

SAW-TOOTH OSCILLATOR Filed Aug. 29, 1940 2 Sheets-Sheet 2 SAW-T @SC'EURHerbert hring, Klein-hnow, Gey;

vested in the Allen Property @ustodian application August 29, 1940,Serial No. 354,743 in Germany September 7, 1939 7 Eiaims.

This invention relates to saw-tooth oscillators and is particularlyconcerned with circuits for producing a saw-tooth current havingsubstantially linear ascending and descending portions. Saw-toothoscillations of this kind are preferably employed for deflecting thecathode ray of cathode ray tubes used in connection with television oroscillograph devices.

It is an object of the invention to provide a saw-tooth oscillatorrequiring a very small amount of energy for its operation. It is afurther object to improve the type of oscillator known as a transformercoupled oscillator conta a transformer with anode windings and gridwindings connected to the anode and grid circuit of an oscillator tube.It is a further obiect to improve circuit arrangements in which a diodeis arranged in parallel to the deflecting coils of the cathode ray tubefor making the slope of the saw-tooth oscillations more linear. Thisdiode has a comparatively large power consumption. Particularly when anoscillator of type is used in receiver circuits it is desirable todevise the circuit in such a manner that the power consumption is as lowas possible.

According to the invention the circuit is arranged in such a manner thatthe biasing potential for the diode is utilized as a part of the anodepotential of the oscillator tube. The operating current flows at leastthrough one winding of the transformer, through the generator tube andthrough the diode. By such an arrangement it is possible to saveapproximately 50% of the power necessary to operate the oscillator. itis furthermore preferable to arrange a. high ohmic resistance inparallel to the biasing condenser of the diode so that a small portionof the current flows through this resistance. The arrangement of thisresistance has the advantage that the oscillator is more readilyself-starting in its operation.

Uther aspects of my invention will be apparent or will be specificallypointed out in the description forming a part of this specification, butI do not limit myself to the embodiment of the invention hereindescribed, as various forms may be adopted within the scope of theclaims.

Referring to the drawings Fig. 1 shows a circuit of a known transformeroscillator,

Fig. 2 shows a circuit arrangement of a sawtooth oscillator contalnlng adiode in parallel to the deflecting coils.

l 3 to ill show circuit arrangements according to the invention.

In order to explain the advantages of the invention reference is made toa known arrangement represented in Fig. 1 containing a so-calledsaw-tooth current oscillator. The anode and grid of an oscillator tube lare connected to two windings of a transformer 2. The grid coil of thetransformer is connected to an element consisting of a condenser hand aresistor i. The deflecting coils t are arranged in parallel to the gridcoil of the transformer. The grid current produces a biasing potentialby means of the resistance capacity element l, 5. The grid cathode spaceof the tube has a linearizing effect upon. the slope of the saw-toothcurrent in the manner of a diode biased by the element consisting ofresistor i and condenser E.

It has been suggested to improve the linearity of the slope by providinga diode ll having a small internal resistance in parallel to thedeflecting coils as shown in Fig. 2. The smoothing condenser 5 of Fig. 1can be omitted and by a suitable choice of resistors d and t the resultcan be obtained that the diode takes over a part of the load. This is ofa considerable advantage for the dimensioning of the oscillator tube.

The arrangement of Fig. 2 has however the drawback that the powerconsumption of the resistor t is lost. Furthermore the voltage acrosselements a and l must be large in comparison to the voltage drop acrossthe diode in order to produce the desired linearizing effect. A powerloss due to the resistor t seems therefore unavoidable.

According to the invention the circuit arrange ment of Fig. 3 or one ofthe following figures is used to overcome this drawback. The anode ofoscillator tube i is connected to the anode winding of transformer i andthe grid of tube i to the grid winding. The deflecting coils 3 areconnected to a. separate output winding. A diode d and a condenser l arearranged in parallel to the deflecting coils l. The biasing resistor lis partly adjustable and comparatively large. It is used for adjustingthe frequency of the oscillator. A condenser ii is provided forsmoothing the anode current. In this arrangement the operating currentflows through the anode winding of the transformer, through theoscillator tube and through the diode. The biasing potential for thediode is therefore used as additional operating anode potential.

As the anode of the diode is directly connected to the cathode of theoscillator tube the two discharge devices can be combined within asingle envelope according to Fig. 4. The diode is arranged within tube iand its anode is the oathode of the oscillator tube.

Instead of arranging the diode in the cathode path of the oscillatortube the diode can also be connected in the anode circuit of this tubeas the grid circuit arrangement having the same sense of winding as thegrid coil. Alsoin this case the anode voltage for the oscillator tubeand the voltage produced across condenser E are arranged in seriesaiding relation so that the external anode voltage supply can be loweredaccordingly. The arrangements of Figs. 6 and 7 have the advantage thatthe cathode of the diode does not require an insulated heater circuitbecause no high tension exists between the filament and the emittinglayer.

In order to enable a centering adjustment of the scanning field upon thescreen of the cathode ray tube the circuit can be arranged according toFig. 8. This circuit is similar to that of Fig. 6 with the exceptionthat an adjustable resistance arrangement I is provided for changing theratio between the grid current flowing through the deflecting coils andthe diode current.

Fig. 9 shows an embodiment in which the deflecting coils are connectedto a separate output winding. The connection between the low potentialside of the deflecting coils and the cathode of the diode and with thepositive pole of the external voltage source as shown in Fig. isreplaced by a connection of the high potential side of the deflectingcoils by way of a choke coil II to the cathode of the oscillator tube I.

A further improvement is represented in Fig. 10. Particularly if thecoils of the transformer are coupled very close the arrangements shownin Figs. 3 to 9 require an impulse for setting the oscillator circuitinto operation. This is necessary because during the heating period ofthe diode the condenser l is not yet charged .to its full operatingvoltage and the grid coil of the transformer is short circuited foralternating currents by way of the diode and the condenser. According toFig. 10 an additional resistor R is arranged in parallel to thecondenser i of the diode circuit. This condenser has the eflect thatduring the heating period an auxiliary current flows which is small incomparison with the operating current so that independent of thecharging of the condenser and the condition of the diode an oscillationcan start. It is preferable to employ an oscillator tube l having ashorter heating period than the diode ii. If the oscillation has oncestarted the condenser receives its charge during the operation and thediode takes over its function. The internal resistance of the diodeassumes a constant low value during the periods of conductivity. Theresistor R can be arranged in similar manner in all circuits of Figs. 3to 9. It can be preferable to employ a voltage divider instead oi. afixed resistor. If a screen grid tube is used for synchronizing purposesthe screen grid potential can be taken off from such a voltage divider.

The invention is not limited to the circuit arrangements shown in thefigures. It can be employed a so in connection with oscillationgenerators of other types. The use of the invention in connection withtransformer oscillators has however the advantage that a simple triodecan be used as oscillator tube consuming only a very small amount ofenergy.

What I claim is:

1. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, means for coupling said anodeand said control element to obtain the transfer of energy therebetween,a deflecting coil, means for coupling said deflecting coil with saidoscillator tube to produce a flow of sawtooth current through said coil,a diode and biasing means comprising a parallel combination of a resist-.ance element and a condenser for providing said diode with an operatingbias voltage connected in series relation, means for connecting saiddiode and said biasing means in parallel relation with said deflectingcoil, a source of operating voltage for said oscillator tube, and meansfor connecting said voltage source and said biasing means inseries-aiding relation between said anode and said cathode.

2. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, a transformer for coupling saidanode and said control element, a deflecting coil coupled to saidtransformer to produce a flow of sawtooth current through said coil, adiode and biasing means comprising a parallel combination of aresistance element and a condenser for providing said diode with anoperating bias voltage connected in series relation, means forconnecting said diode and said biasing means in parallel relation withsaid deflecting coil, a source of operating voltage for said oscillatortube, and means for connecting said voltage source and said biasingmeans in series-aiding relation between said anode and said cathode.

3. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, a transformer for coupling saidanode and said control element, a deflecting coil, means formagnetically coupling said deflecting coil to said transformer toproduce a flow of sawtooth current through said coil, a diode andbiasing means comprising a parallel combination of a resistance elementand a condenser for providing said diode with an operating bias voltageconnected in series relation, means for connecting said diode and saidbiasing means in parallel relation with said deflecting coil, a sourceof operating voltage for said oscillator tube, and means for connectingsaid voltage source and said biasing means in series-aiding relationbetween said anode and said cathode.

4. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, means for coupling said anodeand said control element to obtain the transfer of energy therebetween,a deflecting coil, means for coupling said deflecting coil with saidoscillator tube to produce a flow of sawtooth current through said coil,a diode and biasing means having two terminals and comprising a parallelcombination of a resistance element and a condenser for providing saiddiode with an operating bias voltage connected in series relation, meansfor connecting said diode and said biasing means in parallel relationwith said deflecting coil, a source of operating voltage for saidoscillator tube having two terminals, means for so asoaooe connectingone of said terminals of said biasing means to one of said terminals ofsaid voltage source and the other of said terminals of said biasingmeans to said cathode that the voltages of said source and said biasingmeans are in series-aiding relation.

5. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, means for coupling said anodeand said control element to obtain the transfer of energy therebetween,a deflecting coil, means for coupling said deflecting coil with saidoscillating tube to produce a flow of sawtooth current through saidcoil, a diode and a condenser connected in series relation whereby anoperating bias voltage for said diode is developed across saidcondenser, means for connecting said diode and said condenser inparallel relation with said deflecting coil, a source of operatingvoltage for said oscillator tube, and means for connecting said voltagesource and said condenser in such manner that their voltages are inseries-aiding relation.

6. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, means for coupling said anodeand said control element to obtain the transfer of energy therebetween,a deflecting coil, means for coupling said deflecting coil with saidoscillator tube to produce a flow of sawtooth current through said coil,a diode and a condenser connected in series relation, whereby anoperating bias voltage for said diode is developed across saidcondenser, a resistance element connected to the terminals of saidcondenser, means for connecting said diode and said condenser inparallel relation with saiddeflecting coil, a source of operatingvoltage for said oscillator tube, and means for connecting said voltagesource and said condenser in such manner that their voltages are inseries-aiding relation.

7. A sawtooth current generator comprising an oscillator tube having ananode, a cathode and a control element, a. transformer having a firstwinding and a second winding for coupling said anode and said controlelement, a deflecting coil,

a diode having an anode and a cathode, biasing means comprising aparallel combination of a resistance element and a condenser forproviding said diode with an operating bias voltage con.- nected'inseries relation with said diode, means for connecting said diode cathodeto a point on said first transformer winding, means for coupling saiddeflecting coil with said cathode of said oscillator tube. a source ofoperating voltage for said oscillator tube, said voltage source and saidbiasing means being so connected that their voltages are inseries-aiding relation.

s HERBERT EARRING.

